The invention relates to a distance information system and method for a motor having at least one sensor for measuring the distance between the own motor vehicle and a vehicle situated ahead, having a control unit which is designed for determining as a function of the signals of the sensor whether the measured distance is less than a specified minimum distance for longer than a specified time period, and having at least one optical display, which is activated when it is determined that the measured distance is less than the specified minimum distance for more than a specified time period.
A distance information system in which, in the event of a falling below a specified or determined minimum distance between the motor vehicle and the vehicle situated ahead, an optical display is activated, is known from European Patent Document EP 2 388 160 B1. In order to prevent a constant switching-on and switching-off of the optical display because of the driver's unsteady way of driving and because of measuring inaccuracies, the logic of the distance information system is further developed for providing a hysteresis when determining the minimum distance, so that, as the distance between the motor vehicle and the vehicle situated ahead is increasing, the minimum distance is increased by the hysteresis, and, as the distance is decreasing, the minimum distance is reduced.
Furthermore, vehicles having a distance information system are available in which a corresponding information symbol is displayed when the distance between the motor vehicle and the vehicle situated ahead of it is too small for a specified time period of 2 seconds.
In the case of distance information systems of this type, warnings may possibly occur in certain situations, even though the corresponding situation was knowingly caused by the driver or unintentionally by other traffic participants for a brief time and will rapidly resolve itself again. The driver may perceive these warnings as irritating, whereby the system may lose acceptability and may be switched off.
It is an object of the invention to provide an improved distance information system while taking into account the above problems, which emits a corresponding warning to the driver only when it is actually needed.
This and other objects are achieved according to the invention by a distance information system for a motor vehicle having at least one sensor for measuring the distance between the own motor vehicle and a vehicle situated ahead, having a control unit which is designed for determining as a function of the signals of the sensor whether the measured distance is less than a specified minimum distance for longer than a specified time period, and having at least one optical display, which is activated when it is determined that the measured distance is less than the specified minimum distance for more than a specified time period. The minimum distance and/or the time period is/are specified as a function of a detected or assumed lane change situation.
The at least one sensor may, for example, be a radar or optical sensor, in which case advantageously the sensor system of a cruise control system with a ranging function can be used, which is present in the vehicle anyhow. The values for the minimum distance and the time period required for determining the necessity of activating the optical display can be stored in a corresponding characteristic diagram and/or can be determined or specified, as required, as a function of additional parameters, such as the current speed. In a correct sense, the minimum distance is a time gap within which the vehicle reaches the position of the vehicle situated ahead. The device for the optical display may be a so-called head-up display, so that, when the optical display is activated, a warning symbol is displayed directly in the driver's field of vision.
The invention is based on the recognition that, specifically in lane-change situations, the distance between the motor vehicle (the “own” motor vehicle) and the vehicle situated ahead is considerably reduced for a short time, which is, however, either knowingly caused by the driver or unintentionally by another traffic participant and is relatively rapidly resolved. In order to prevent a warning which, in such situations, may be perceived by the driver as annoying, the distance information system is further developed according to the invention such that the minimum distance and/or the time period is specified as a function of a detected or assumed lane-change situation, or is adapted as a function of a detected or assumed lane-change situation. However, it should thereby also still be ensured that, in actually critical situations (for example, a very short distance or driving for a long time at a short distance), a warning will still be triggered.
Depending on the lane-change situation, different, particularly advantageous adaptations of the minimum distance and/or time period can be used.
In a first category of lane-change situations, all lane-change situations of the own motor vehicle are to be subsumed. Since, especially in the case of lane-change situations caused by the driver himself, under certain circumstances, a tailgating with respect to the vehicle situated ahead is knowingly caused by the driver, it is particularly advantageous for the minimum distance and/or the time period to be specified or adapted as a function of a detected or assumed lane-change situation of the own vehicle. Therefore, in the case of a detected or assumed overtaking lane-change situation of the own motor vehicle, advantageously, a smaller minimum distance and/or a longer time period is specified, or the currently applicable minimum distance is reduced and/or the currently applicable time period is extended, so that a brief closing-in on the actual vehicle situated ahead which may often be the case, in overtaking situations—is not judged to be critical and the optical warning is not triggered. A reduction of the minimum distance ensures that, before the overtaking operation, the driver can tailgate with respect to the vehicle situated ahead without triggering a warning. However, it is simultaneously ensured that, in the event of an excessive tailgating, thus when there is a falling below the reduced minimum distance, a warning will still be emitted. By means of a prolongation of the defined time period for which there has to be a falling below the minimum distance before a warning is emitted, a warning can also be prevented for the time period of the tailgating before the actual overtaking operation. However, if the overtaking operation is not terminated or the lane change is not initiated, a warning is emitted if the driver does not again enlarge the distance from the vehicle situated ahead.
Such an overtaking lane-change operation can be recognized or assumed at an early point-in-time by analyzing different parameters. Ideally, an overtaking lane-change situation is detected or assumed as a function of the acceleration of the motor vehicle and/or of a turn signal activity, an overtaking lane-change situation being detected or at least assumed when a (significant) acceleration of the own vehicle and a turn signal operation is determined. As required, the (relative) lateral movement of the vehicle toward the lane boundary or to the vehicle situated ahead can also be evaluated.
In a second category of lane-change situations, all lane-change situations of other traffic participants are to be subsumed. These may be so-called veering-out lane-change situations of traffic participants in the own driving lane, which change to another lane, or so-called veering-in lane change situations of traffic participants to neighboring lanes, which change to the own lane. In the case of such lane-change operations, situations may unintentionally occur in which, in the case of a conventional layout of a distance information system, a warning is generated for the driver. However, such situations are rapidly resolved again by the driver or as a result of the manner of driving of the other traffic participants, so that, as a rule, a warning does not seem necessary. In order to avoid such normally not necessary warnings, it is particularly advantageous for the minimum distance and/or the time period to be specified or adapted as a function of a detected or assumed lane change situation of the vehicle situated ahead or of a vehicle situated in a neighboring lane, which changes to the own lane. In veering-in lane-change situations, it is particularly advantageous to enlarge the time window because, as a rule, although the veering-in vehicle penetrates into the minimum-distance area, this situation will be relatively rapidly resolved by the driver by a corresponding driving behavior.
In the case of a detected or assumed veering-out lane-change situation of the vehicle situated ahead or in the case of a detected or assumed veering-in lane-change situation of a vehicle situated in the neighboring lane into the lane of the own motor vehicle, a smaller minimum distance and/or a longer time period is therefore advantageously specified or the actually applicable minimum distance is reduced and/or the actually applicable time period is prolonged, so that a brief closer tailgating or a longer-lasting falling below a conventionally specified minimum distance with respect to the current vehicle situated ahead—which may often occur particularly in the case of so-called veering-in vehicles—is not judged to be a critical situation and the optical warning is not triggered.
A veering-out lane-change situation of the vehicle situated ahead or a veering-in lane-change situation of a vehicle situated in the neighboring lane can be detected or assumed at an early point in time by evaluating different parameters. Ideally, a veering-out lane-change situation of the vehicle situated ahead or a veering-in lane-change situation of a vehicle situated in the neighboring lane is determined or assumed as a function of the lateral movement, particularly the relative lateral movement of the vehicle situated ahead or of the relevant vehicle situated in the neighboring lane with respect to the own vehicle.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.